Joint for coaxial conductor electric cables



June 1, 1948. B|RKBY JoIu-r FOR (JO-AXIAL connuc'ron BLEc'rnIc cumsFiled Jan. 4, 1945 H lll In water H away Run-BY Ay Attorney PatentedJune 1, 1948 JOINT FOR COAXIAL CONDUCTO ELECTRIC CABLES Harold Birkby,London, England, assignor to Standard Telephones and Cables Limited,London, England, a company of Great Britain Application January 4, 1945,Serial No. 571,220 In Great Britain January 15, 1944 3 Claims. 1

This invention relates to joints for coaxial conductor electric cablesand has for its object to provide an improved joint which is ofcomparatively simple form and which will, however, be of satisfactorymechanical strength and will prevent the passage of water past the jointin the event that a cable length suffers damage.

According to the present invention we provide a joint for a coaxialconductor cable in which insulating spacing members between coaxialinner and outer portions of the Joint are used, which spacing membersare provided with channels filled with a plastic insulating substancewhich adheres to the said inner and outer portions and so seals thejoint.

The invention will be better understood from the following descriptiontaken in conjunction with the accompanying drawing.

Fig 1 is aside elevational view of a portion of coaxial cable includinga joint according to the present invention, parts thereof being brokenaway to facilitate understanding of certain structural features, and vFig. 2 is a longitudinal sectional view of a cable similar to that shownin Fig. 1.

The lengths of coaxial cable to be joined are illustrated as of the typein which an inner conductor I is held in spaced relation with a co axialouter conductor by means of spacing insulating discs I3. Theouterconductor comprises a metal tape formed into a tube as described in U.S. Patent No. 2,126,290, granted August 9, 1938, and spaced away fromthe inner conductor by insulating washers I3. The cable is provided withouter helical screening tapes I.

To prepare the two lengths of cable for jointing the outer screeningtapes I of each length are bound'near the end with an adhesive paperbinder 2 and are then spot soldered as shown at 3 to the outer conductor5 of the cable. The screening tapes I are then cut oflf just beyond thebinder 2. A metal collar 4 is sweated on to the outer conductor 5, oneend of the collar having a tapered internal diameter to fit over theportion 6 of the screening tapes I that is beyond the binder 2. Theouter conductor 5 is then cut off flush with the collar I.

To make the joint, an insulating annular member I provided with a cavitycontaining a plastic cement 8 is inserted over each inner conductor IIIso as to fit within the outer conductor 5. In each annular member thecavity containing the cement 8 is connected to the inner bore of theannular member by radial openings II. The plastic cement 8 is composedof a material 2 easily melted and thus caused to flow through the radialopenings II to adhere to the inner conductor I0 and also caused toadhere to the outer conductor 5. It is preferred to use a mixture ofshellac and tricresyl phosphate which will be caused to flow by thesubsequent operations incidental to the making of the joint. The annularmembers I are formed with end flanges as shown to butt against the endsof the outer conductors 5 and collars 4.

The centrally located conductors are then cut to butt each other at thejoint and are joined by sweating a split copper ferrule I2 around themat the place of abutment. A split copper ferrule II having its edgesmade to overlap at I5 is placed so that its ends overlap the collars 4and is then sweated to them and the overlapping edges of the ferrule I4are sweated together. Screening tapes I6 are then attached by solderingas indicated at 9 at one end to the original screening tapes I, and arethen wrapped over the whole joint in the same lap as the screening tapesI and attached by soldering to the original screening tapes I at theother end of the joint. Only a portion of these tapes is shown in thedrawing. Q

It is clear that various minor modifications may be made in the abovedescribed structure and the method of constructing same. ample, theouter ferrule It may be seamless and sweated on to the collars 4, or itmay be internally screw threaded and the collars 4 externally screwthreaded. It is also clear that the joint according to the invention maybe formed between lengths of coaxial electric conductor cable of othertypes than that referred to above.

The same ratio of internal diameter of outer conductor to externaldiameter of inner conductor is not preserved throughout the joint abovedescribed, but the length of the joint and the departure from the ratiois so small that the transmission characteristics of the completed cableare not appreciably afiected.

What is claimed is:

1. An end-piece for a coaxial cable that comprises a flanged cylindricalmemberformed of electrically insulative material and having a portionthereof adapted to being received within the open end of the externalconductor of a coaxial cable, said member having an axially locatedopening adapted to receive the internal conductor of the coaxial cableand having radially extending channels communicating with said axiallylocated opening and terminating in a peripheral groove formed in theportion of said For ex- 'radially 3 member which is adapted to beingreceived in the open end of the external conductor oi the coaxial cable,and a plastic mass within said extending channels and peripheral groove.capable oi contacting and adhering to the central conductor and theexternal conductor of the coaxial cable to term a fluid-tight closure.

2. An end-piece tor a coaxial'cable that comprises a flanged plugadapted to being titted within the open end at the external conductor ofa coaxial cable and having an opening through which the internalconductor oi. the cable may extend, said plug having a. peripheralgroove i'ormed therein in the portionto be disposed within the externalconductofand having radially extending channels communicating with thegroove, and a plastic mass within said channels and groove capable ofcontacting and adhering to the conductors of the cable to provide afluidtight closure.

3. In combination with a coaxial cable having I a tubular externalconductor andan internal conductor positioned axially within theexternal conductor, a closure plug that comprises a cylindrical membertermed oi electrieally insulative material having a portion iittingwithin the open and oi the external conductor and provided with a flangeabutting against the end or said conductor, said plug having an axiallyextending opening through which the internal conductor projects andwhich communicates through radial channels with a peripheral grooveformed in the portion 0! said plug within the end of the externalconductor, and a plastic mass disposed within said channels and groovecontacting and adhering to the internal and external conductor to eflectfluid-tight closure of the cable end.

HAROLD BlRKBY.

RWENURS are The following references are of record in the tile oi thispatent:

UNITED STATES FATWTS Number Name Date 2,152,504 Scott et al. Mar, 28,1939 2,243,881 Peters et al. June 8. 1941

